title: Induction of Rhizopus oryzae germination under starvation using host metabolites increases spore susceptibility to heat stress.
abstract: Sweetpotato is a nutritional source worldwide. Soft rot caused by Rhizopus spp. is a major limiting factor in the storage of produce, rendering it potentially unsafe for human consumption. In this study, Rhizopus oryzae was used to develop a concept of postharvest disease control by weakening the pathogen through induction of spore germination under starvation conditions. We isolated the sweetpotato active fractions (SPAFs) that induce spore germination and used them at a low dose to enhance spore weakening caused by starvation. Germination in SPAF at 1 mg/ml weakened the pathogen spores by delaying their ability to form colonies on rich media and by increasing their sensitivity to heat stress. The weakening effect was also supported by reduced metabolic activity, as detected by Alarmar Blue fluorescent dye assays. Spores incubated with SPAF at 1 mg/ml showed DNA fragmentation in some of their nuclei, as observed by TUNEL assay. In addition, these spores exhibited changes in ultrastructural morphology (i.e., shrinkage of germ tubes, nucleus deformation, and vacuole formation) which are hallmarks of programmed cell death. We suggest that induction of spore germination under starvation conditions increases their susceptibility to stress and, therefore, might be considered a new strategy for pathogen control.
authors.forename: Tidhar
authors.initials: T
authors.lastname: Turgeman
authors.forename: Nathan
authors.initials: N
authors.lastname: Kakongi
authors.forename: Avishai
authors.initials: A
authors.lastname: Schneider
authors.forename: Yakov
authors.initials: Y
authors.lastname: Vinokur
authors.forename: Paula
authors.initials: P
authors.lastname: Teper-Bamnolker
authors.forename: Shmuel
authors.initials: S
authors.lastname: Carmeli
authors.forename: Maggie
authors.initials: M
authors.lastname: Levy
authors.forename: Christopher D
authors.initials: CD
authors.lastname: Skory
authors.forename: Amnon
authors.initials: A
authors.lastname: Lichter
authors.forename: Dani
authors.initials: D
authors.lastname: Eshel
mesh_terms: D017209:Apoptosis; D053938:DNA Fragmentation; D004305:Dose-Response Relationship, Drug; D006358:Hot Temperature; D027723:Ipomoea batatas / Q000737:chemistry* / Q000382:microbiology; D010935:Plant Diseases / Q000382:microbiology*; D010936:Plant Extracts / Q000302:isolation & purification / Q000494:pharmacology*; D012233:Rhizopus / Q000166:cytology / Q000187:drug effects* / Q000235:genetics / Q000502:physiology; D013172:Spores, Fungal / Q000187:drug effects* / Q000502:physiology
chemical_list: D010936:Plant Extracts